Catalysts are substances which accelerate chemical reaction, but subsequently are not a part of products of reaction. The quantitative and qualitative structure of catalysts remains invariable in the course of a catalysis.
Types of catalysts
Catalysts provide faster result of any chemical reaction. Reacting with initial substances of reaction, the catalyst forms with them intermediate connection then this connection is exposed to transformation and as a result breaks up to the necessary final product of reaction and also to the catalyst which did not undergo changes. After disintegration and formation of a necessary product the catalyst reacts with initial reagents, forming increasing number of initial substance again. This cycle can be repeated millions of times and if to remove the catalyst from group of reagents, reaction can last in hundreds and thousands of times more slowly.
Catalysts are heterogeneous and homogeneous. Heterogeneous catalysts during chemical reaction form an independent phase which is separated by the dividing border from a phase of initial reagents. Homogeneous catalysts, on the contrary, are a part of the same phase with initial reagents.
There are catalysts of organic origin which participate in fermentation and maturing, they are called enzymes. Without their direct participation the mankind could not receive the most part of alcoholic drinks, lactic products, products from the test and also honey and jam. Without participation of enzymes the metabolism at living organisms would be impossible.
Requirements to substances to catalysts
Catalysts which are widely used in industrial production have to have a number of the properties necessary for a successful completion of reaction. Catalysts have to be highly active, selective, mechanically strong and heat-resistant. They have to possess long action, easy regeneration, catalytic poisons resistance, hydrodynamic properties and also the small price.
Modern use of industrial catalysts
In the current high-tech production the catalysts are used when cracking oil products, receiving aromatic hydrocarbons and high-octane gasoline, receiving pure hydrogen, oxygen or inert gases, ammonia synthesis, receiving sulphurous and sulfuric acid without additional expenses. Also catalysts are widely used to receiving nitric acid, ethylene, phthalic anhydride, methyl and ethyl alcohol and ethyl aldehyde. The most widely used catalysts are a metal platinum, vanadium, nickel, chrome, iron, zinc, silver, aluminum and palladium. Some salts of these metals are also quite often applied.